1. Field of the Invention
The present invention relates to a carbon nanotube synthesizing apparatus.
2. Description of the Related Art
Conventionally, there has been known a method for synthesizing carbon nanotubes oriented in a perpendicular direction on a substrate using a plasma CVD (for example, see Science, 282, 1105, (1998)). The carbon nanotubes oriented in the perpendicular direction on the substrate are used for, for example, multi-walled carbon nanotubes for a field emitter.
According to the method using the plasma CVD, a field improvement effect by a sheath formed by plasma has been considered to contribute to the orientation of carbon nanotubes. However, the method using the plasma CVD has a problem that while carbon radicals are generated in a plasma generation area, the substrate is attacked by ions generated as a by-product of the carbon radicals, so that growing carbon nanotubes are etched. Accordingly, the method using the plasma CVD is disadvantageous in growing long carbon nanotubes, and is more disadvantageous in the case of single-walled carbon nanotubes because single-walled carbon nanotubes are more easily subjected to etching than multi-walled nanotubes.
To solve the above described problem, the inventors has proposed a carbon nanotube synthesizing apparatus configured to, in an antenna-type plasma CVD, hold a substrate in a position at a distance from an antenna which allows the substrate to avoid being attacked by ions that are generated as a by-product of radicals generated by plasma generated at the antenna and allows the substrate to be reached by the radicals kept in a radical state (see Japanese Patent Laid-open No. 2006-36593). According to the above described carbon nanotube synthesizing apparatus, attack by ions originated from plasma can be prevented, and the substrate is not exposed to an unnecessarily high temperature, and therefore it is possible to manufacture oriented carbon nanotubes formed from long single-walled carbon nanotubes.
However, the above described conventional carbon nanotube synthesizing apparatus has a disadvantage that the quality of manufactured oriented carbon nanotubes is not enough.